The present invention relates generally to the field of lithium anodes for use in electrochemical cells. More particularly, the present invention pertains to an anode for use in an electrochemical cell comprising a first layer comprising lithium metal in contact with three or more overlying layers interposed between the lithium-containing layer and a non-aqueous electrolyte. The present invention also pertains to methods of forming such anodes, electrochemical cells comprising such anodes, and methods of making such cells.
Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
There has been considerable interest in recent years in developing high energy density batteries with lithium containing anodes. Lithium metal is particularly attractive as the anode of electrochemical cells because of its extremely light weight and high energy density, compared for example to anodes, such as lithium intercalated carbon anodes, where the presence of non-electroactive materials increases weight and volume of the anode, and thereby reduces the energy density of the cells, and to other electrochemical systems with, for example, nickel or cadmium electrodes. Lithium metal anodes, or those comprising mainly lithium metal, provide an opportunity to construct cells which are lighter in weight, and which have a higher energy density than cells such as lithium-ion, nickel metal hydride or nickel-cadmium cells. These features are highly desirable for batteries for portable electronic devices such as cellular phones and laptop computers where a premium is paid for low weight. Unfortunately, the reactivity of lithium and the associated cycle life, dendrite formation, electrolyte compatibility, fabrication and safety problems have hindered the commercialization of lithium cells.
The separation of a lithium anode from the electrolyte of the cell is desirable for reasons including the prevention of dendrites during recharging, reaction with the electrolyte, and cycle life. For example, reactions of lithium anodes with the electrolyte may result in the formation of resistive film barriers on the anode. This film barrier increases the internal resistance of the battery and lowers the amount of current capable of being supplied by the battery at the rated voltage.
Many different solutions have been proposed for the protection of lithium anodes including coating the lithium anode with interfacial or protective layers formed from polymers, ceramics, or glasses, the important characteristic of such interfacial or protective layers being to conduct lithium ions. For example, U.S. Pat. Nos. 5,460,905 and 5,462,566 to Skotheim describe a film of an n-doped conjugated polymer interposed between the alkali metal anode and the electrolyte. U.S. Pat. No. 5,648,187 to Skotheim and U.S. Pat. No. 5,961,672 to Skotheim et al. describe an electrically conducting crosslinked polymer film interposed between the lithium anode and the electrolyte, and methods of making the same, where the crosslinked polymer film is capable of transmitting lithium ions. U.S. Pat. No. 5,314,765 to Bates describes a thin layer of a lithium ion conducting ceramic coating between the anode and the electrolyte. Yet further examples of interfacial films for lithium containing anodes are described, for example, in: U.S. Pat. Nos. 5,387,497 and 5,487,959 to Koksbang; U.S. Pat. No. 4,917,975 to De Jonghe et al.; U.S. Pat. No. 5,434,021 to Fauteux et al.; and U.S. Pat. No. 5,824,434 to Kawakami et al.
A single protective layer of an alkali ion conducting glassy or amorphous material for alkali metal anodes, for example, in lithium-sulfur cells, is described in U.S. Pat. No. 6,02,094 to Visco et al. to address the problem of short cycle life.
Despite the various approaches proposed for methods for forming lithium anodes and the formation of interfacial or protective layers, there remains a need for improved methods, which will allow for increased ease of fabrication of cells, while providing for cells with long cycle life, high lithium cycling efficiency, and high energy density.
The anode of the present invention for use in an electrochemical cell comprises: (i) a first anode active layer comprising lithium metal; and (ii) a multi-layer structure in contact with a surface layer of the first anode active layer; wherein the multi-layer structure comprises three or more layers, wherein each of the three or more layers comprises a layer selected from the group consisting of single ion conducting layers and polymer layers. In one embodiment, the multi-layer structure comprises four or more layers.
In one embodiment of the present invention, an anode for use in an electrochemical cell, comprises an anode active layer, which anode active layer comprises: (i) a first layer comprising lithium metal; and (ii) a second layer of a temporary protective material in contact with a surface of the first layer. In one embodiment, the temporary protective material is a temporary protective metal that is capable of forming an alloy with lithium metal or is capable of diffusing into lithium metal.
In one embodiment, the temporary protective metal is selected from the group consisting of copper, magnesium, aluminum, silver, gold, lead, cadmium, bismuth, indium, gallium, germanium, zinc, tin, and platinum In one embodiment, the temporary protective metal is copper.
In one embodiment, the thickness of the first layer is 2 to 100 microns.
In one embodiment, the thickness of the second layer is 5 to 500 nanometers. In one embodiment, the thickness of the second layer is 20 to 200 nanometers.
In one embodiment, the anode further comprises a substrate, wherein the substrate is in contact with a surface of the first layer on the side opposite the second layer. In one embodiment, the substrate comprises a current collector. In one embodiment, the substrate is selected from the group consisting of metal foils, polymer films, metallized polymer films, electrically conductive polymer films, polymer films having an electrically conductive coating, electrically conductive polymer films having an electrically conductive metal coating, and polymer films having conductive particles dispersed therein.
In one embodiment, the anode further comprises a third layer, the third layer comprising a single ion conducting layer, wherein the third layer is in contact with the second layer on the side opposite to the first layer. In one embodiment, the single ion conducting layer of the third layer comprises a glass selected from the group consisting of lithium silicates, lithium borates, lithium alumninates, lithium phosphates, lithium phosphorus oxynitrides, lithium silicosulfides, lithium germanosulfides, lithium lanthanum oxides, lithium tantalum oxides, lithium niobium oxides, lithium titanium oxides, lithium borosulfides, lithium aluminosulfides, and lithium phosphosulfides and combinations thereof. In one embodiment, the single ion conducting layer of the third layer comprises a lithium phosphorus oxynitride.
In another embodiment, the anode further comprises a third layer, the third layer comprising a polymer, and wherein the third layer is in contact with the second layer on the side opposite to the first layer. In one embodiment, the polymer of the third layer is selected from the group consisting of electrically conductive polymers, ionically conductive polymers, sulfonated polymers, and hydrocarbon polymers. In one embodiment, the electrically conductive polymer is selected from the group consisting of poly(p-phenylene), polyacetylene, poly(phenylenevinylene), polyazulene, poly(perinaphthalene), polyacenes, and poly(naphthalene-2,6-diyl). In one embodiment, the polymer of the third layer is a crosslinked polymer.
In one embodiment, the anode further comprises a fourth layer, wherein the fourth layer is in contact with the third layer on the side opposite to the second layer. In one embodiment, the fourth layer comprises a polymer. In one embodiment, the polymer of the fourth layer is selected from the group consisting of electrically conductive polymers, jonically conductive polymers, sulfonated polymers, and hydrocarbon polymers. In one embodiment, the polymer of the fourth layer is a crosslinked polymer. In one embodiment, the fourth layer comprise a metal.
In one embodiment, the thickness of the third layer is in the range of 5 to 5000 nanometers. In one embodiment, the thickness of the fourth layer is in the range of 5 to 5000 nanometers.
Another aspect of the present invention pertains to methods of preparing an anode for use in an electrochemical cell, wherein the anode comprising an anode active layer, as described herein, is formed by the steps of:
(a) depositing onto a substrate, as described herein, a first layer comprising lithium metal, as described herein; and
(b) depositing over the first layer a second layer of a temporary protective metal, as described herein;
wherein the temporary protective metal is capable of forming an alloy with lithium metal or is capable of difflusing into lithium metal.
In one embodiment, the temporary protective metal is selected from the group consisting of copper, magnesium, aluminum, silver, gold, lead, cadmium, bismuth, indium, gallium, germanium, zinc, tin, and platinum.
In one embodiment, the first layer is deposited in step (a) by a method selected from the group consisting of thermal evaporation, sputtering, jet vapor deposition, laser ablation, and extrusion.
In one embodiment, the second layer is deposited in step (b) by a method selected from the group consisting of thermal evaporation, sputtering, jet vapor deposition, laser ablation, and extrusion.
In one embodiment, the method comprises after step (b), a step (c) of depositing a third layer comprising a single ion conducting layer, as described herein, over the second layer. In one embodiment, the third layer is deposited by a method selected from the group consisting of sputtering, thermal evaporation, laser ablation, chemical vapor deposition, and jet vapor deposition.
In another embodiment, the method comprises after step (b), a step (c) of depositing a third layer comprising a polymer, as described herein, over the second layer. In one embodiment, the third layer is deposited by a method selected from the group consisting of thermal evaporation, sputtering, laser ablation, chemical vapor deposition, and jet vapor deposition. In one embodiment, the polymer of the third layer is deposited by the method of flash evaporation.
In another embodiment, the method of the present invention comprises, after step (c), a step (d) of depositing a fourth layer, wherein said fourth layer comprises a polymer.
Another aspect of the present invention pertains to an electrochemical cell comprising: (a) a cathode comprising an electroactive sulfuir-containing material; (b) an anode; and (c) a non-aqueous electrolyte interposed between the anode and the cathode, wherein the anode comprises: (i) a first anode active layer comprising lithium metal; and (ii) a multi-layer structure in contact with a surface layer of the anode active layer, wherein the multi-layer structure comprises three or more layers, wherein each of the three or more layers comprises a layer selected from the. group consisting of single ion conducting layers and polymer layers.
In one embodiment, the thickness of the first anode active layer is from 2 to 100 microns.
In one embodiment, the thickness of the multi-layer structure is 0.5 to 10 microns. In one embodiment, the thickness of the multi-layer structure is 1 to 5 microns.
In one embodiment, the multi-layer structure comprises four or more layers.
In one embodiment, the multi-layer structure further comprises a metal alloy layer, wherein the metal alloy comprises a metal selected from the group consisting of Zn, Mg, Sn, and Al.
In one embodiment, the polymer layer of the multi-layer structure comprises a polymer layer formed from the polymerization of one or more acrylate monomers selected from the group consisting of alkyl acrylates, glycol acrylates, and polyglycol acrylates. In one embodiment, the single ion conducting layer of the multi-layer structure comprises a glass selected from the group consisting of lithium silicates, lithium borates, lithium aluminates, lithium phosphates, lithium phosphorus oxynitrides, lithium silicosulfides, lithium germanosulfides, lithium lanthanum oxides, lithium tantalum oxides, lithium niobium oxides, lithium titanium oxides, lithium borosulfides, lithium aluminosulfides, and lithium phosphosulfides and combinations thereof. In one embodiment, the single ion conducting layer comprises a lithium phosphorus oxynitride.
In one embodiment, the non-aqueous electrolyte is a liquid.
In one embodiment, the first anode active layer firther comprises an intermediate layer of a temporary protective metal layer or a plasma CO2 treatment layer, which intermediate layer is interposed between the first anode active layer and the multi-layered structure.
In one embodiment, the electroactive sulfur-containing material of the cathode comprises elemental sulfur. In one embodiment, the electroactive sulfur-containing material comprises an electroactive sulfur-containing organic polymer, wherein the sulfur-containing organic polymer, in its oxidized state, comprises one or more polysulfide moieties, xe2x80x94Smxe2x80x94, where m is an integer equal to or greater than 3. In one embodiment, the cathode active material comprises an electroactive sulfur-containing organic polymer, wherein the sulfur-containing organic polymer, in its oxidized state, comprises one or more polysulfide moieties, xe2x80x94Smxe2x88x92 where m is an integer equal to or greater than 3. In one embodiment, the cathode active material comprises an electroactive sulfuir-containing organic polymer, wherein the sulfur-containing organic polymer, in its oxidized state, compnses one or more polysulfide moieties, SM2xe2x88x92where m is an integer equal to or greater than 3.
A further aspect of the present invention pertains to an electrochemical cell comprising:
(a) a cathode comprising a cathode active material;
(b) an anode; and
(c) a non-aqueous electrolyte interposed between the anode and the cathode;
wherein the anode comprises an anode active layer, which anode active layer comprises:
(i) a first layer comprising lithium metal, as described herein; and
(ii) a second layer of a temporary protective metal, as described herein, in contact with a surface of the first layer;
wherein the temporary protective metal is capable of forming an alloy with lithium or is capable of diffusing into lithium metal.
In one embodiment, the temporary protective metal is characterized by forming an alloy with, dissolving into, blending with, or diffusing into the lithium metal of the first layer during electrochemical cycling of the cell.
In one embodiment, the temporary protective metal is characterized by forming an alloy with, dissolving in, blending with, or diffusing into the lithium metal of the first layer prior to electrochemical cycling of the cell.
In one embodiment of the cell of the present invention, the anode further comprises a substrate, as described herein.
In one embodiment of the cell of the present invention, the anode further comprises a third layer comprising a single ion conducting layer, as described herein. In one embodiment, the anode further comprises a third layer comprising a polymer, as described herein.
In one embodiment of the cell of the present invention, the electrolyte is selected from the group consisting of liquid electrolytes, solid polymer electrolytes, and gel polymer electrolytes. In one embodiment, the electrolyte comprises a separator selected from the group consisting of polyolefin separators and microporous xerogel layer separators.
In one embodiment of the cell of the present invention, the cathode active material comprises one or more materials selected from the group consisting of electroactive metal chalcogenides, electroactive conductive polymers, and electroactive sulfur-containing materials, and combinations thereof.
In one embodiment, the cathode active material comprises electroactive sulfur-containing materials, as described herein.
In one embodiment, the cell is a secondary cell. In one embodiment, the cell is a primary cell.
Another aspect of the present invention pertains to a method for making an electrochemical cell, as described herein, the method comprising the steps of:
(a) providing a cathode comprising a cathode active material, as described herein;
(b) providing an anode, wherein the anode comprises an anode active layer, which anode active layer comprises:
(i) a first layer comprising lithium metal, as described herein; and
(ii) a second layer of a temporary protective metal, as described herein, in contact with a surface of the first layer; and
(c) providing a non-aqueous electrolyte, as described herein, wherein the electrolyte is interposed between the anode and the cathode;
wherein the temporary protective metal is capable of forming an alloy with lithium metal or is capable of diffusing into lithium metal.
In one embodiment of the methods of making an electrochemical cell, the temporary protective metal is characterized by forming an alloy with, dissolving in, blending with, or diffusing into the lithium metal of the first layer during electrochemical cycling of the cell.
In one embodiment of the methods of making an electrochemical cell, the temporary protective metal is characterized by forming an alloy with, dissolving in, blending with, or diffusing into the lithium metal of the first layer prior to electrochemical cycling of the cell.
In one embodiment of the methods of making an electrochemical cell, the anode further comprises a third layer, the third layer comprising a material selected from the group consisting of single ion conducting materials, as described herein, and polymers, as described herein, wherein the third layer is in contact with the temporary protective metal layer on the side opposite to the first layer comprising lithium.
In one embodiment of the methods of making an electrochemical cell, the anode comprises a fourth layer, as described herein.
As will be appreciated by one of skill in the art, features of one aspect or embodiment of the invention are also applicable to other aspects or embodiments of the invention.